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                <h2 id="Android-网络与数据的存储"><a href="#Android-网络与数据的存储" class="headerlink" title="Android 网络与数据的存储"></a>Android 网络与数据的存储</h2><p>使用SharedPerferences方便地存储数据<br>数据持久化<br>适用于存储一些简单的数据</p>
<p>public class ListViewDemoActivity extends Activity implements View.OnClickListener {</p>
<pre><code>public static final String LIST_VIEW_DATA_COUNTS = &quot;list_view_data_counts&quot;;
public static final String PREFERENCE_NAME = &quot;preference_name&quot;;
public static final int DEFAULT_VALUE = 10;
//ListView视图作为一个容器，房子
private ListView mphoneBookListView;
private List&lt;UserInfo&gt; mUserInfos;
private int mDataCounts = 10;
private Button mConfirmButton;
private PhoneBookAdapter mPhoneBookAdapter;
private EditText mDataCountsEditText;
private SharedPreferences mSharedPreferences;

@Override
protected void onCreate(Bundle savedInstanceState) &#123;
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_listview_demo);
    findViews();
    setData();
    setListeners();


&#125;

private void findViews() &#123;
    mphoneBookListView = findViewById(R.id.list_view);
    mDataCountsEditText = findViewById(R.id.data_counts_edit_text);
    mConfirmButton = findViewById(R.id.confirm_button);
&#125;

private void setData() &#123;
    //每次创建时读取
    SharedPreferences sharedPreferences = getSharedPreferences(PREFERENCE_NAME,Context.MODE_PRIVATE);

    mDataCounts = sharedPreferences.getInt(LIST_VIEW_DATA_COUNTS, DEFAULT_VALUE);

    mDataCountsEditText.setText(String.valueOf(mDataCounts));
    mUserInfos = new ArrayList&lt;&gt;();

    for (int index = 0; index &lt; mDataCounts; index++) &#123;
        mUserInfos.add(new UserInfo(&quot;西门吹雪&quot;, 18));

    &#125;


    //数据列表和数据绑定,adapter适配器，房子里的柜子，柜子放进房子
    mPhoneBookAdapter = new PhoneBookAdapter(ListViewDemoActivity.this, mUserInfos);
    //房子(mphoneBookListView)里面有柜子(phoneBookAdapter)，柜子里面有格子(name_text_view)，
    //格子里面放数据private String[] mNames = &#123;&quot;西门吹雪&quot;,&quot;李寻欢&quot;&#125;
    mphoneBookListView.setAdapter(mPhoneBookAdapter);
&#125;


private void setListeners() &#123;
    //刷新更新数据
    mPhoneBookAdapter.notifyDataSetChanged();
    //条目点击事件
    mphoneBookListView.setOnItemClickListener(new AdapterView.OnItemClickListener() &#123;
        @Override
        public void onItemClick(AdapterView&lt;?&gt; parent, View view, int position, long id) &#123;
            //点击第一条数据时更新
            if(position==0)&#123;
                // 新建另外一批数据
                mUserInfos.clear();
                mUserInfos.add(new UserInfo(&quot;我是新数据一&quot;,20));
                mUserInfos.add(new UserInfo(&quot;我是新数据二&quot;,20));
                mUserInfos.add(new UserInfo(&quot;我是新数据三&quot;,20));
                // 替换掉老的数据,数据通过PhoneBookAdapter传递,因此要在PhoneBookAdapter中创建refreshData方法
                // 刷新ListView,让他更新自己的视图
                mPhoneBookAdapter.refreshData(mUserInfos);
            &#125;


            Toast.makeText(ListViewDemoActivity.this, mUserInfos.get(position).getmUserName()+&quot;被点击了&quot;,Toast.LENGTH_LONG).show();
        &#125;
    &#125;);
    //长按事件
    mphoneBookListView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() &#123;
        @Override
        public boolean onItemLongClick(AdapterView&lt;?&gt; parent, View view, int position, long id) &#123;
            Toast.makeText(ListViewDemoActivity.this, mUserInfos.get(position).getmUserName()+&quot;被长按了&quot;,Toast.LENGTH_LONG).show();
            return false;
        &#125;
    &#125;);

    // 给确认按钮设置点击事件
    mConfirmButton.setOnClickListener(this);

&#125;


@Override
public void onClick(View v) &#123;
    switch (v.getId())&#123;
        case R.id.confirm_button:
            //点击确认时,首先取到输入的数字
            mDataCounts= Integer.valueOf(mDataCountsEditText.getText().toString());
            refreshListView();

            //保存起来,不然editText设置了2,退出后回来还是原来地个数,因此要保存起来,下次打开时自动读取
            saveData2Preference(mDataCounts);
            break;
    &#125;


&#125;

private void saveData2Preference(int dataCounts) &#123;

    // 系统会自动帮我们创建一个XML文件,名字是&quot;preference_name&quot;,地址在Data/Data/Shard_prefs
    mSharedPreferences = getSharedPreferences(PREFERENCE_NAME, Context.MODE_PRIVATE);

    SharedPreferences.Editor editor = mSharedPreferences.edit();
    //数据持久化地存起来了
    editor.putInt(LIST_VIEW_DATA_COUNTS,dataCounts);
    
</code></pre>
<p>&#x2F;&#x2F;        删除<br>&#x2F;&#x2F;        editor.remove(LIST_VIEW_DATA_COUNTS);</p>
<pre><code>    //与commit不同,apply后台写数据,另开线程,和网络相关和IO操作相关的都要用异步的apply
    editor.apply();

&#125;

private void refreshListView() &#123;
    //刷新数据
    mUserInfos.clear();
    for (int index = 0; index &lt; mDataCounts; index++) &#123;
        mUserInfos.add(new UserInfo(&quot;李寻欢&quot;, 18));

    &#125;

    mPhoneBookAdapter.refreshData(mUserInfos);
    mPhoneBookAdapter.notifyDataSetChanged();
&#125;
</code></pre>
<p>}</p>
<hr>
<p> <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="条数"
        android:id="@+id/data_counts"/></p>
<pre><code>&lt;EditText
    android:layout_width=&quot;200dp&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:layout_below=&quot;@+id/data_counts&quot;
    android:id=&quot;@+id/data_counts_edit_text&quot;
    /&gt;
&lt;Button
    android:layout_width=&quot;wrap_content&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:text=&quot;确定&quot;
    android:layout_toRightOf=&quot;@+id/data_counts_edit_text&quot;
    android:id=&quot;@+id/confirm_button&quot;/&gt;

&lt;TextView
    android:id=&quot;@+id/phone_text_view&quot;
    android:layout_width=&quot;wrap_content&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:layout_centerHorizontal=&quot;true&quot;
    android:layout_below=&quot;@+id/data_counts_edit_text&quot;
    android:text=&quot;@string/phone_book&quot;/&gt;






&lt;ListView
    android:layout_width=&quot;match_parent&quot;
    android:layout_height=&quot;match_parent&quot;
    android:layout_below=&quot;@+id/phone_text_view&quot;
    android:id=&quot;@+id/list_view&quot;&gt;
&lt;/ListView&gt;
</code></pre>
<hr>
<p>作业：做一个小应用，启动时有两张引导界面，只有第一次启动时，显示，看完后下一次就不显示了</p>
<h2 id="如何随己所欲管理文件"><a href="#如何随己所欲管理文件" class="headerlink" title="如何随己所欲管理文件"></a>如何随己所欲管理文件</h2><p>&#x2F;&#x2F;测试文件, 自己用file创建文件<br>    private void testFileDemo() {<br>        &#x2F;&#x2F;在internal storage里创建了一个新文件<br>        File file &#x3D; new File(getFilesDir(),”test.txt”);</p>
<pre><code>    Log.i(&quot;MainActivity&quot;,&quot;getFilesDir:&quot;+ getFilesDir().getAbsolutePath());
    Log.i(&quot;MainActivity&quot;,&quot;file path:&quot;+file.getAbsolutePath());

    String string = &quot;I am handsome&quot;;

    try &#123;
        boolean isSucess = file.createNewFile();
    &#125; catch (IOException e) &#123;

        Log.i(&quot;MainActivity&quot;,&quot;test.txt create error:&quot;+e.toString());

        e.printStackTrace();
    &#125;


    try &#123;
        FileOutputStream fileOutputStream = openFileOutput(&quot;test2.txt&quot;, Context.MODE_PRIVATE);
        fileOutputStream.write(string.getBytes());
    &#125; catch (FileNotFoundException e) &#123;
        e.printStackTrace();
    &#125; catch (IOException e) &#123;
        e.printStackTrace();
    &#125;
    
    //检查 external storage 是否可用
    String state = Environment.getExternalStorageState();
    
    if(TextUtils.equals(state,Environment.MEDIA_MOUNTED))&#123;
        
    &#125;
    
&#125;
</code></pre>
<hr>
<p>操作assets目录下的文件</p>
<pre><code>void testAssets() throws IOException &#123;
    //assets下的文件不会被编译改变

    //第一种,直接读路径
    WebView webView = new WebView(this);
    webView.loadUrl(&quot;file:///android_asset/HelloWorld.html&quot;);

    //open的只能是文件,不能是文件夹
    //读网页
    InputStream inputStream = getResources().getAssets().open(&quot;HellowWorld.html&quot;);


    //读列表
</code></pre>
<p>&#x2F;&#x2F;        String[] fileNames &#x3D; getAssets().list(“images&#x2F;“);</p>
<pre><code>    //读图片

    InputStream IMGinputStream = getAssets().open(&quot;images/dog.jpg&quot;);
    //把图片转为bitmap
    Bitmap bitmap = BitmapFactory.decodeStream(IMGinputStream);
    ImageView imageView = new ImageView(this);
    imageView.setImageBitmap(bitmap);


    //读音乐
    AssetFileDescriptor assetFileDescriptor = getAssets().openFd(&quot;bgm.mp3&quot;);
    MediaPlayer player = new MediaPlayer();
    player.reset();
    player.setDataSource(assetFileDescriptor.getFileDescriptor(),assetFileDescriptor.getStartOffset(),assetFileDescriptor.getLength());
    player.prepare();
    player.start();

&#125;
</code></pre>
<hr>
<p>操作raw目录下的文件  操作res目录下的文件<br>    void testResFile(){<br>        &#x2F;&#x2F;读音乐<br>        InputStream inputStream &#x3D; getResources().openRawResource(R.raw.bgm);</p>
<pre><code>    //读color
    getResources().getColor(R.color.blue);
    //读String
    getResources().getString(R.string.app_name)
&#125;
</code></pre>
<hr>
<p>操作sd卡(外部存储)文件<br>    void testSDCard(){<br>&#x2F;&#x2F;        File file &#x3D; new File(“&#x2F;sdcard&#x2F;test&#x2F;a.txt”);&#x2F;&#x2F;直接写路径,不推荐<br>        String filePath &#x3D; Environment.getExternalStorageDirectory().getAbsolutePath();<br>        File file &#x3D; new File(filePath);</p>
<pre><code>    Environment.getDataDirectory(); //获取安卓中的data数据目录
    Environment.getDownloadCacheDirectory(); //获取安卓中download目录 ...
    
&#125;
</code></pre>
<hr>
<p>drawable放图片,mipmap放头像,layout放布局,values放值</p>
<p>相同点和区别:<br>放在assets和raw下的文件创建apk时都会原封不动地打在包里,不会再编译成二进制<br>但是assets是纯原封不动,raw系统会自动映射到R文件里的id,可以直接通过R.引用<br>res中不可以再有目录结构</p>
<h2 id="SQLite数据库"><a href="#SQLite数据库" class="headerlink" title="SQLite数据库"></a>SQLite数据库</h2><p>特色： 轻量级，独立，隔离，跨平台，多语言接口，安全性<br>对象关系映射ORM<br>public class DatabaseActivity extends AppCompatActivity {</p>
<pre><code>private SQLiteDatabase mSqLiteDatabase;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) &#123;
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_database);

    //新建一个数据库文件
    DatabaseHelper databaseHelper = new DatabaseHelper(this);
    mSqLiteDatabase = databaseHelper.getWritableDatabase();


    //Add
    findViewById(R.id.add_button).setOnClickListener(new View.OnClickListener() &#123;
        @Override
        public void onClick(View v) &#123;
            //IO操作,建议后台操作,直接在onClick里操作容易卡死

            //新建键值对
            ContentValues contentValues = new ContentValues();
            contentValues.put(DatabaseHelper.USERNAME, &quot;无名剑主&quot;);
            contentValues.put(DatabaseHelper.PASSWORD, &quot;1234567&quot;);

            long rowNumber = mSqLiteDatabase.insert(DatabaseHelper.TABLE_NAME, null, contentValues);

            if (rowNumber != -1) &#123;
                Toast.makeText(DatabaseActivity.this, &quot;插入成功&quot;, Toast.LENGTH_SHORT).show();
            &#125;


            queryData();

        &#125;
    &#125;);


    findViewById(R.id.delete_button).setOnClickListener(new View.OnClickListener() &#123;
        @Override
        public void onClick(View v) &#123;
            //Delete


            String whereClauseString = &quot;username=?&quot;;
            String[] whereArgsString = &#123;&quot;无名剑主&quot;&#125;;
            mSqLiteDatabase.delete(DatabaseHelper.TABLE_NAME, whereClauseString, whereArgsString);


            queryData();
        &#125;
    &#125;);


    findViewById(R.id.update_button).setOnClickListener(new View.OnClickListener() &#123;
        @Override
        public void onClick(View v) &#123;
            //Update

            ContentValues contentValues = new ContentValues();
            contentValues.put(DatabaseHelper.PASSWORD, &quot;7654321&quot;);
            String whereClauseString = &quot;username=?&quot;;
            String[] whereArgsString = &#123;&quot;无名剑主&quot;&#125;;
            mSqLiteDatabase.update(DatabaseHelper.TABLE_NAME, contentValues, whereClauseString, whereArgsString);


            queryData();
        &#125;
    &#125;);


    //事务，批量操作

    //开始事务,此时数据库就会被锁定
    mSqLiteDatabase.beginTransaction();
    try &#123;
        //需要的操作

        mSqLiteDatabase.setTransactionSuccessful();
    &#125; catch (Exception e)&#123;
        e.printStackTrace();
    &#125;finally &#123;
        mSqLiteDatabase.endTransaction();
    &#125;
&#125;
private void queryData() &#123;
    //Query

    //游标
    Cursor cursor =    mSqLiteDatabase.query(DatabaseHelper.TABLE_NAME,null,null,null,null,null,null,null);

    if(cursor.moveToFirst())&#123;
        int count = cursor.getCount();
        for (int i = 0; i &lt; count; i++) &#123;
            String userName = cursor.getString(cursor.getColumnIndexOrThrow(DatabaseHelper.USERNAME));
            String password = cursor.getString(cursor.getColumnIndexOrThrow(DatabaseHelper.PASSWORD));

            Log.i(MainActivity.class.getSimpleName(),i+&quot;:&quot;+userName+&quot;||&quot;+password);
        &#125;
    &#125;
&#125;
</code></pre>
<h2 id=""><a href="#" class="headerlink" title="}"></a>}</h2><p>public class DatabaseHelper extends SQLiteOpenHelper {</p>
<pre><code>public static final String TABLE_NAME = &quot;user&quot;;
public static final String USERNAME = &quot;username&quot;;
public static final String PASSWORD = &quot;password&quot;;
public static final String DATABASE_NAME = &quot;test.db&quot;;

public DatabaseHelper(Context context) &#123;
    super(context, DATABASE_NAME, null, 1);
&#125;

@Override
public void onCreate(SQLiteDatabase db) &#123;
    //新建表
    db.execSQL(&quot;create table &quot; + TABLE_NAME + &quot;(&quot; + USERNAME + &quot; varchar(20) not null,&quot; + PASSWORD + &quot; varchar(60) not null);&quot;);

&#125;

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) &#123;
    //升级数据库
&#125;
</code></pre>
<h2 id="-1"><a href="#-1" class="headerlink" title="}"></a>}</h2><pre><code>&lt;Button
    android:id=&quot;@+id/add_button&quot;
    android:layout_width=&quot;match_parent&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:text=&quot;Add&quot; /&gt;

&lt;Button
    android:id=&quot;@+id/delete_button&quot;
    android:layout_width=&quot;match_parent&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:text=&quot;Delete&quot; /&gt;

&lt;Button
    android:id=&quot;@+id/update_button&quot;
    android:layout_width=&quot;match_parent&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:text=&quot;Update&quot; /&gt;
</code></pre>
<hr>
<h2 id="Content-Provider"><a href="#Content-Provider" class="headerlink" title="Content Provider"></a>Content Provider</h2><p>四大组件之一（activity，service，broadcast receiver）<br>应用程序间共享数据的一种方式<br>为存储和获取数据提供了统一的接口<br>Android为常见的一些数据提供了默认的ContentProvider</p>
<p>定义：<br>Content Provider 将一些特定的应用程序数据供给其他应用程序使用<br>数据可以存储于文件系统，SQLite数据库或其他方式<br>内容提供者继承于ContentProvider 基类，为其他应用程序取用和存储他管理的数据实现了一套标准方法<br>应用程序并不能直接调用这些方法，而是使用ContentResolver对象，调用他的方法作为替代<br>ContentResover可以与任意内容提供者进行会话，与其合作来对所有相关交互通讯进行管理</p>
<hr>
<p>public class URIList {</p>
<pre><code>public static final String CONTENT = &quot;content://&quot;;
//包名
public static final String AUTHORITY = &quot;com.example.sqtian&quot;;
//表面
public static final String USER_URI = CONTENT + AUTHORITY + &quot;/&quot; + DatabaseHelper.USER_TABLE_NAME;
public static final String BOOK_URI = CONTENT + AUTHORITY + &quot;/&quot; + DatabaseHelper.BOOK_TABLE_NAME;
</code></pre>
<p>}</p>
<hr>
<p>public class DatabaseHelper extends SQLiteOpenHelper {</p>
<pre><code>public static final String USER_TABLE_NAME = &quot;user_table_name&quot;;
public static final String USERNAME = &quot;username&quot;;
public static final String PASSWORD = &quot;password&quot;;
public static final String DATABASE_NAME = &quot;test.db&quot;;
public static final String BOOK_TABLE_NAME = &quot;book_table_name&quot;;
public static final String BOOK_NAME = &quot;book_name&quot;;
public static final String BOOK_PRICE = &quot;book_price&quot;;

public DatabaseHelper(Context context) &#123;
    super(context, DATABASE_NAME, null, 1);
&#125;

@Override
public void onCreate(SQLiteDatabase db) &#123;
    //新建表
    db.execSQL(&quot;create table &quot; + USER_TABLE_NAME + &quot;(&quot; + USERNAME + &quot; varchar(20) not null,&quot; + PASSWORD + &quot; varchar(60) not null);&quot;);
    db.execSQL(&quot;create table &quot; + BOOK_TABLE_NAME + &quot;(&quot; + BOOK_NAME + &quot; varchar(20) not null,&quot; + BOOK_PRICE + &quot; varchar(60) not null);&quot;);


&#125;

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) &#123;
    //升级数据库
&#125;
</code></pre>
<p>}</p>
<hr>
<p>public class TestContentProvider extends ContentProvider {</p>
<pre><code>private static UriMatcher sUriMatcher;
private static final int URI_MATCH_USER = 1;
private static final int URI_MATCH_BOOK = 2;

static &#123;
    sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

    // 将content://com.example.sqtian/user_table_name 用int URI_MATCH_USER来代表
    // 将content://com.example.sqtian/book_table_name 用int URI_MATCH_BOOK来代表
    sUriMatcher.addURI(URIList.AUTHORITY, DatabaseHelper.USER_TABLE_NAME,URI_MATCH_USER);
    sUriMatcher.addURI(URIList.AUTHORITY, DatabaseHelper.BOOK_TABLE_NAME,URI_MATCH_BOOK);
&#125;

private DatabaseHelper mDatabaseHelper;


//用代号进行匹配,传入uri得到表名
private String getTableName(Uri uri)&#123;
    int type = sUriMatcher.match(uri);
    String tableName = null;
    switch(type)&#123;
        case URI_MATCH_USER:
            tableName = DatabaseHelper.USER_TABLE_NAME;
            break;
        case URI_MATCH_BOOK:
            tableName = DatabaseHelper.BOOK_TABLE_NAME;
            break;
    &#125;
    return tableName;
&#125;

@Override
public boolean onCreate() &#123;

    mDatabaseHelper = new DatabaseHelper((getContext()));
    return false;
&#125;

@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) &#123;
    //实现自己的query方法

    //先通过uri得知是那张表
    String tableName = getTableName(uri);
    if(TextUtils.isEmpty(tableName))&#123;
        return null;
    &#125;

    Cursor cursor = mDatabaseHelper.getWritableDatabase()
            .query(tableName,projection,selection,selectionArgs,null,null,sortOrder);

    return cursor;
&#125;

@Nullable
@Override
public String getType(@NonNull Uri uri) &#123;
    return null;
&#125;

@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) &#123;
    String tableName = getTableName(uri);
    if(TextUtils.isEmpty(tableName))&#123;
        return null;
    &#125;

    long id = mDatabaseHelper.getWritableDatabase().insert(tableName,null,values);

    //返回一个uri和id拼接后的结果
    return ContentUris.withAppendedId(uri,id);
&#125;

@Override
public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) &#123;
    String tableName = getTableName(uri);
    if(TextUtils.isEmpty(tableName))&#123;
        return -1;
    &#125;

    int count = mDatabaseHelper.getWritableDatabase().delete(tableName, selection, selectionArgs);
    //返回的是改变的条数
    return count;
&#125;

@Override
public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) &#123;
    String tableName = getTableName(uri);
    if(TextUtils.isEmpty(tableName))&#123;
        return -1;
    &#125;

    int count = mDatabaseHelper.getWritableDatabase().update(tableName,values,selection,selectionArgs);
    //返回的是改变的条数
    return count;
&#125;
</code></pre>
<p>}</p>
<hr>
<pre><code>    //内容解析器
    ContentResolver contentResolver = getContentResolver();
</code></pre>
<p>&#x2F;&#x2F;        &#x2F;&#x2F;资源路径<br>&#x2F;&#x2F;        &#x2F;&#x2F;content:&#x2F;&#x2F;package_name&#x2F;table_name&#x2F;id&#x2F;row_name<br>&#x2F;&#x2F;        Uri uri &#x3D; Uri.parse(“content:&#x2F;&#x2F;com.android.contacts&#x2F;contacts”);</p>
<pre><code>    //游标
    Cursor cursor = contentResolver.query(Uri.parse(URIList.USER_URI),null,null,null,null);
</code></pre>
<p>&#x2F;&#x2F;        if(cursor !&#x3D; null &amp;&amp; cursor.moveToFirst()){<br>&#x2F;&#x2F;            &#x2F;&#x2F;遍历把数据取出来<br>&#x2F;&#x2F;        }</p>
<pre><code>    // ContentProvider 提供者 提供增删改查的方法,query(uri)...
</code></pre>
<hr>
<h2 id="网络与数据处理"><a href="#网络与数据处理" class="headerlink" title="网络与数据处理"></a>网络与数据处理</h2><p>public class NetworkActivity extends Activity implements View.OnClickListener {</p>
<pre><code>private Button mButton;
private TextView mTextView;
private EditText mEditText;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) &#123;
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_network);

    findViews();

    mButton.setOnClickListener(this);

    String url = getEditTextUrl();
&#125;

private void findViews() &#123;
    mEditText = findViewById(R.id.address_edit_text);
    mTextView = findViewById(R.id.result_text);
    mButton = findViewById(R.id.get_data_button);



&#125;

private String getEditTextUrl() &#123;

    return mEditText != null? mEditText.getText().toString():&quot;&quot;;

&#125;

@Override
public void onClick(View v) &#123;
    switch (v.getId())&#123;
        case R.id.get_data_button:
            String url = getEditTextUrl();
            //请求网络数据,需要manifest设置网络权限
            String data = requestData(url);
</code></pre>
<p>&#x2F;&#x2F;                mTextView.setText(data); 放到异步操作中去处理</p>
<pre><code>            new RequestNstworkDataTask().execute(url);
            break;
    &#125;
&#125;

private String requestData(String urlString) &#123;

    try &#123;
        URL url = new URL(urlString);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setConnectTimeout(30000);
        connection.setRequestMethod(&quot;GET&quot;);

        connection.connect();
        int responseCode = connection.getResponseCode();
        String responseMessage = connection.getResponseMessage();

        InputStream inputStream = connection.getInputStream();
        Reader reader = new InputStreamReader(inputStream,&quot;UTF-8&quot;);
        char[] buffer = new char[1024];
        reader.read(buffer);
        String content = new String(buffer);

        return content;


    &#125; catch (MalformedURLException e) &#123;
        e.printStackTrace();
    &#125; catch (IOException e) &#123;
        e.printStackTrace();
    &#125;


    return null;
&#125;

//异步任务处理,同步会卡死

class RequestNstworkDataTask extends AsyncTask&lt;String,Integer,String&gt; &#123;


    //在后台work之前


    @Override
    protected void onPreExecute() &#123;
        super.onPreExecute();
        //主线程
    &#125;

    @Override
    protected String doInBackground(String[] params) &#123;

        String result = requestData(params[0]);
        return null;
    &#125;


    @Override
    protected void onPostExecute(String result) &#123;
        super.onPostExecute(result);
        //执行完之后在主线程中
        mTextView.setText(result);

    &#125;
&#125;
</code></pre>
<h2 id="-2"><a href="#-2" class="headerlink" title="}"></a>}</h2><pre><code>&lt;EditText
    android:id=&quot;@+id/address_edit_text&quot;
    android:layout_width=&quot;match_parent&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:hint=&quot;请输入网址&quot;
    android:layout_gravity=&quot;center_horizontal&quot;
    /&gt;

&lt;Button
    android:layout_width=&quot;match_parent&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:text=&quot;获取数据&quot;
    android:layout_gravity=&quot;center_horizontal&quot;
    android:id=&quot;@+id/get_data_button&quot;/&gt;
&lt;TextView
    android:layout_width=&quot;wrap_content&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:id=&quot;@+id/result_text&quot;
    android:text=&quot;This is Result&quot;/&gt;
    
    
    
</code></pre>
<hr>
<h2 id="xml解析"><a href="#xml解析" class="headerlink" title="xml解析"></a>xml解析</h2><p>test.xml<br><?xml version="1.0" encoding="utf-8"?><br><web><br>    <item id="0" url="http://www.baidu.com">百度</item><br>    <item id="1" url="http://www.taobao.com">淘宝</item><br>    <item id="2" url="http://www.qq.com">腾讯</item><br>    <item id="3" url="http://www.zhihu.com">知乎</item></p>
</web>
--------------------------------------------------------------------------
public class WebURL {

<pre><code>private int mID;
private String mUrl;
private String mContent;

public int getID() &#123;
    return mID;
&#125;

public void setID(Integer ID) &#123;
    mID = ID;
&#125;

public String getUrl() &#123;
    return mUrl;
&#125;

public void setUrl(String url) &#123;
    mUrl = url;
&#125;

public String getContent() &#123;
    return mContent;
&#125;

public void setContent(String content) &#123;
    mContent = content;
&#125;
</code></pre>
<h2 id="-3"><a href="#-3" class="headerlink" title="}"></a>}</h2><h2 id="SAX"><a href="#SAX" class="headerlink" title="SAX"></a>SAX</h2><p>首先得到一个XMLReader，然后setContentHandler</p>
<hr>
<p>public class SAXParseHandler extends DefaultHandler {</p>
<pre><code>public static final String ITEM = &quot;item&quot;;
List&lt;WebURL&gt; mWebURLS;
WebURL mWebURL;

@Override
public void startDocument() throws SAXException &#123;
    super.startDocument();

    mWebURLS = new ArrayList&lt;&gt;();
&#125;

@Override
public void endDocument() throws SAXException &#123;
    super.endDocument();
&#125;

@Override
public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException &#123;
    super.startElement(uri, localName, qName, attributes);
    mWebURL = new WebURL();
    if(TextUtils.equals(localName, ITEM))&#123;
        for (int i = 0; i &lt; attributes.getLength(); i++) &#123;
            if(TextUtils.equals(attributes.getLocalName(i),&quot;id&quot;))&#123;
                mWebURL.setID(Integer.valueOf(attributes.getValue(i)));
            &#125;
            //不同的属性情况
            
            
        &#125;
    &#125;

&#125;

@Override
public void endElement(String uri, String localName, String qName) throws SAXException &#123;
    super.endElement(uri, localName, qName);
&#125;

@Override
public void characters(char[] ch, int start, int length) throws SAXException &#123;
    super.characters(ch, start, length);
&#125;

public List&lt;WebURL&gt; gerXMLList() &#123;
    return mWebURLS;
&#125;
</code></pre>
<p>}</p>
<hr>
<p>&#x2F;&#x2F; parse file by SAX, SAX方法解析XML<br>    private void testSAXParse() throws ParserConfigurationException, SAXException, IOException {</p>
<pre><code>    //首先创建一个工厂,从工厂里取出一个解析器,解析器读出一个reader
    SAXParserFactory saxParserFactory = SAXParserFactory.newInstance();
    SAXParser saxParser = saxParserFactory.newSAXParser();
    XMLReader xmlReader = saxParser.getXMLReader();

    //给reader设置处理器
    SAXParseHandler saxParseHandler = new SAXParseHandler();
    xmlReader.setContentHandler(saxParseHandler);

    //给reader数据流
    InputStream inputStream = getResources().openRawResource(R.raw.test);
    InputSource inputSource = new InputSource(inputStream);
    xmlReader.parse(inputSource);

    //得到数据
    saxParseHandler.gerXMLList();

&#125;
</code></pre>
<hr>
<p>PULL</p>
<pre><code>    //pull xml里才能读
    XmlResourceParser xmlResourceParser = getResources().getXml(R.xml.test);
    try &#123;
        while(xmlResourceParser.getEventType() != XmlResourceParser.END_DOCUMENT) &#123;
            if (xmlResourceParser.getEventType() == XmlResourceParser.START_TAG)&#123;
                String tagName = xmlResourceParser.getName();
                if(TextUtils.equals(tagName,&quot;item&quot;))&#123;
                    String id = xmlResourceParser.getAttributeValue(null,&quot;id&quot;);
                &#125;
            &#125;
        &#125;
    &#125; catch (XmlPullParserException e) &#123;
            e.printStackTrace();
    &#125;
</code></pre>
<p>DOM</p>
<h2 id="JSON"><a href="#JSON" class="headerlink" title="JSON"></a>JSON</h2><pre><code>    //JSON
    InputStream is = getResources().openRawResource(R.raw.json);
    String jsonString = getStringByInputStream(is);

    try &#123;
        JSONObject jsonObject = new JSONObject(jsonString);
        String title = jsonObject.getString(&quot;title&quot;);

        JSONObject userJSONObject = jsonObject.getJSONObject(&quot;user&quot;);
        userJSONObject.getLong(&quot;id&quot;);

        JSONArray jsonArray = jsonObject.getJSONArray(&quot;images&quot;);

    &#125; catch (JSONException e) &#123;
        e.printStackTrace();
    &#125;
</code></pre>
<p>GSON<br>        &#x2F;&#x2F;GSON<br>        Gson gson &#x3D; new Gson();</p>
<pre><code>    //fromJson() 把JsonString变成一个对象
    UserData userData = gson.fromJson(jsonString, UserData.class);
    
</code></pre>
<hr>
<p>public class UserData {<br>    &#x2F;&#x2F;json.txt中对应的属性</p>
<pre><code>//SerializedName注解对应

@SerializedName(&quot;title&quot;)
private String mTitle;

@SerializedName(&quot;content&quot;)
private String mContent;

@SerializedName(&quot;user&quot;)
private User mUser;

@SerializedName(&quot;images&quot;)
private List&lt;String&gt; mImages;

public class User&#123;
    @SerializedName(&quot;id&quot;)
    private long mID;

    @SerializedName(&quot;name&quot;)
    private String mName;

    @SerializedName(&quot;avatar&quot;)
    private String mAvatar;
&#125;
</code></pre>
<p>}</p>
<p>网络状态处理<br>    ConnectivityManager<br>    NetworkInfo</p>
<p>public class NetworkUtil {</p>
<pre><code>public void testNetwork(Context context)&#123;
    //回答网络连接的查询结果,并在网络连接改变时通知应用程序
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    boolean isWifiConnection = networkInfo.isConnected();
</code></pre>
<p>&#x2F;&#x2F;        networkInfo &#x3D; connectivityManager.getAllNetworkInfo(ConnectivityManager.TYPE_MOBILE);<br>    }<br>}</p>

                
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